Aspects of the present invention relate to Digital Subscriber Line (DSL). Other aspects of the present invention relate to establishing a DSL connection.
In today's highly competitive telecommunication market, new services with varying levels of grades are offered everyday. Alternatives to the conventional telephony include Internet services with narrow band or broad band options. Digital Subscriber Line (DSL) provides an alternative to broadband Internet services using conventional telephone lines.
To received DSL service, a customer premise equipment (CPE) must be installed at a user's premise. Through the CPE, the user can establish a DSL connection with a central office via a DSL Access Module (DSLAM) installed at the central office. The CPE at the user's site and the DSLAM at the central office establish a DSL connection by communicating with each other via a DSL data link layer protocol. Examples of such a protocol include High-level Data Link Control (HDLC, International Organization for Standardization, ISO/IEC 3309:1993(E)), Asynchronous Transfer Mode layer specification (ATM cell, International Telecommunication Union, ITU-T Recommendation I.361 (February 1999)-B-ISDN ATM Layer Specification, located at http://www.itu.int/itudoc/itu-t/rec/i/s_i361.htm), Asynchronous Transfer Mode Forum, and Frame-based User-Network Interface (ATM FUNI, The ATM Forum Technical Committee, defined in Frame Based User-To-Network Interface Specification v2.0, AF-SAA-0088.000, July 1997, located at ftp://ftp.atmforum.com/pub/approved-specs/af-saa-0088.000.pdf). Most DSLAM vendors support more than one DSL data link layer protocols.
The DSL data link layer protocol used between a particular CPE and a DSLAM is usually defined via DSL data link layer protocol provisioning when a user initially subscribes the service. Once a DSL data link layer protocol is chosen to facilitate the communication between a particular CPE and the DSLAM, it is used whenever a DSL connection needs to be established. That is, when the user associated with the CPE requests DSL service, the CPE and the DSLAM rely on the DSL data link layer protocol agreed during the DSL data link layer protocol provisioning to facilitate the requested service.
One problem associated with this pattern of operation is that a mismatch in DSL data link layer protocol may occur between the CPE and the DSLAM. The mismatch may be due to different reasons. For example, it may be caused by a simple configuration error at the central office. The mismatch may also occur when either the DSLAM at the central office or the CPE at user's site is upgraded (e.g., to support more advanced DSL data link layer protocols). When a mismatch occurs, the DSL connection can not be established because the CPE and the DSLAM will not be able to communicate. In this case, the service is not delivered and overall service quality degrades.
Available solution to this problem is to perform a manual trial-and-error trouble-shooting on all possible DSL data link layer protocols until successful link synchronization is achieved. Such a manual solution is, although technologically trivial, time consuming and costly.